Lead from a Roman ship to be used for hunting neutrinos

Italy's National Institute of Nuclear Physics, at its laboratories in Gran
Sasso, has received 120 lead bricks from an ancient Roman ship that sunk
off of the coast of Sardinia 2,000 years ago. The ship's cargo was
recovered 20 years ago, thanks to the contribution of the INFN, which at
the time received 150 of these bricks. The INFN is now receiving
additional bricks to complete the shield for the CUORE experiment, which
is being conducted to study extremely rare events involving neutrinos.
After 2,000 years under the sea, this lead will now be used to perform a
task 1,400 metres under the Apennine mountain.

The National Laboratories of Gran Sasso (LNGS) of Italy's National
Institute of Nuclear Physics (INFN) has received 120 2,000-year-old lead
bricks from the National Archaeological Museum of Cagliari in Sardinia.
The lead bricks, together with the ship that transported them, had
remained in the sea for 2,000 years, which reduced by approximately
100,000 times the albeit very low original radioactivity represented by
one of its radionuclides, lead-210. In fact, lead-210 has a half-life of
22 years, so that by now it has practically disappeared in the bricks.

It is precisely this characteristic that makes the lead extremely useful,
in that it can be used to perfectly shield experiments of extreme
precision, such as those conducted in the underground INFN laboratories in
Gran Sasso. After 2,000 years under the sea, this lead will now be used to
perform a task 1,400 metres under the Apennine mountain.

The part of the bricks that is "adorned" with inscriptions will be removed
and conserved, whereas the remaining part will be cleaned of incrustations
and melted to construct a shield for the international experiment CUORE, a
study on neutrinos, whose discoveries could contribute to the knowledge of
this elusive particle and of the evolution of the Universe.

Moreover, the INFN will perform important precise measures on the lead
(and possibly on the copper found on the ship), to study the materials
used in the Bronze Age.

The lead bricks were made available as the result of a 20-year
collaboration involving the INFN, its facilities in Cagliari, and the
Archaeological Superintendency of Cagliari, with the support of the
General Direction of Antiquity. As part of this collaboration, 20 years
ago the INFN contributed 300 million lira for the excavation of the ship
and the recovery of its cargo.

The INFN would like to thank the superintendents Drs. Fulvia Lo Schiavo
and Marco Minoja, as well as Doctor Donatella Salvi, for their
collaboration.

"The commander of that ship would certainly never have imagined that the
lead would be used 2,000 years later for something that had to do with the
Universe and the stars" - comments INFN President Roberto Petronzio -
"History and Science can now speak to one another across the centuries,
thanks to the research in High-Energy Physics".

"This lead," - explains Professor Ettore Fiorini - "which is responsible
for the CUORE experiment, represents an extremely important material for
shielding the apparatuses used to conduct research on rare events - a
material that must be totally free of radioactive contamination".

Lucia Votano, Director of the INFN laboratories in Gran Sasso, explains
that "it's great and unique that the most advanced and innovative
technologies must rely on archaeology and the technology of the ancient
Romans. The ancient lead recoverd from the bottom of the sea will be
essential for protecting the experiment from natural radioactivity, which
could obscure the rare process of neutrinoless double beta decay".

Twenty years ago, an amateur scuba diver swimming off the coast of
Oristano found a "navis oneraria magna", a 36-metre Roman ship dating back
more than 2,000 years - between 80 and 50 BC - whose cargo consisted of a
thousand lead forms. The ship had come from the area of the Sierra de
Cartagena, in present-day Spain, and was probably headed towards Rome. In
its hull, on a floor of copper, there were approximately 2000 lead bricks,
together with various types of amphoras, four anchors, rigging, and
everyday objects. The ship sank near the island that is today known as Mal
di Ventre, a little more than one mile from the shore. Because the anchors
were still in the prow and the bricks were in part still stacked,
archaeologists believe that the ship sank without undergoing any sort of
trauma and for reasons that are difficult to determine (perhaps
intentionally sunk by the ship's commander himself). The relic and all
that it contained remained under more than 30 metres of water on the sandy
sea floor for 2000 years.

The lead

The lead bricks weigh about 33 kg each and are 46 centimetres long and
nine centimetres thick. The weight corresponds to 100 Roman pounds, which
by law was the maximum weight that could be carried by a slave.

The lead was a byproduct of silver extraction, yet in Roman times the
market for lead was extremely important, given that it was widely used to
produce everyday objects, such as water ducts, weights, and urns, and in
the production of bronze coins and of the lead bullets for slings, a
weapon used in battle by soldiers in ancient Rome. More than 200 of these
bullets were found on the sunken ship.

Each brick is engraved with an indication of who manufactured it, for
example, Caius and Marcus Pontilieni, sons of Marcus; Quintus Appius, son
of Caius; and Carulius Hispalius. These were families of Italian origin
who were involved in mining in Spain. In various areas in the
Mediterranean, archaeologists have found materials produced by the
Pontilieni family and Caulius Hispalius, whereas Quintus Appius was
unknown. Ancient lead is particularly useful not only for Physics
experiments but also for certain uses in Information Technology. For this
reason, throughout the world, lead found in ancient sunken ships (from the
European galleons of the 15th century onwards to the ancient ships that
sailed the Mediterranean Sea) is sought after.

The CUORE experiment

The CUORE experiment at the INFN National Laboratories in Gran Sasso is
seeking to discover an extremely rare process known as "neutrinoless
double beta decay", which would allow researchers to not only directly
measure the mass of neutrinos but also to determine whether or not they
are Majorana particles (i.e., with coinciding particles and
anti-particles).

The extremely important implications of this experiment regard the world
of both the infinitesimally small (i.e., that of elementary subatomic
particles) and the infinitely large (i.e., the Universe and its
evolution).

The CUORE experiment represents the most recent and ambitious development
of the technique of bolometer of tellurium dioxide, with which the INFN
has over 20 years of experience.